Today's post concludes Exercise 10 - this is the second half of the exercise and involves building the circuit shown on page 81 and taking some readings of the amps flowing through two different locations on the breadboard.
First off... this exercise was very frustrating. Not because the circuit is incorrect, but because it took me forever to figure out that my cheapy, non-ranging multimeter wasn't up to the task of providing me with any readings... only after switching to my autoranging (and manually switching it to mA reading) did I start to get useful readings.
Once again, I had to modify the circuit a bit because I lacked those pesky 180 ohm resistors... I just substituted 220 ohm resistors in their place. I didn't get the readings indicated in the book, but that makes sense given that I've put more resistance in the circuit.
You'll have to look close at my photos to figure out which is which - you can use the location of where I place the probes to match them up to the proper location (A1 or A2). This is where having those patch wires is really handy - I used a bunch of them to connect the potentiometer to various components... I also used small pieces of stripped 22 gauge wires as places to touch the probes... again, look closely and you should see how I did it.
My maximum A2 reading (with the potentiometer wide open) was around 16mA... reading at A1 (potentiometer wide open) was .53mA. These readings are very odd, but then again, my circuit has some variations in resistance AND my AC Adapter is putting out about 12.25 volts... and it's Tuesday. Weird things happen on Tuesdays.
Anyway, on to Exercise 11...